My guess is that it has been altered in some way. It looks well used. Had it been a backup chip it would not have gotten that much use. It would be great if you could get a high resolution scan of the thing.

Another thing about it is that it still has a white inlay. All of their house chips had inlays that matched the color of the chip. The $, $5, $25, $100 and on up were all done this way. Maybe someone plopped it into some Rit dye or something.

Greg